1. Field of the Invention
This invention relates, generally, to wave energy conversion devices that convert abundant natural energy present in oceans and other bodies of water into electrical or chemical energy such as the creation of hydrogen from water through electrolysis.
2. Description of the Prior Art
Water turbines have been used to extract useful energy from moving water, or water under pressure, for thousands of years. Many different types of water turbines have been invented and used in the past to extract energy from water under a variety of circumstances, and characterized by a variety of characteristics, with optimal efficiencies. e.g., Francis turbines, Pelton turbines, Kaplan turbines, etc.
The design of water turbines is a mature discipline. Most modern turbines convert the kinetic or potential energy of water into rotary motion which can be used to create electricity with efficiencies that exceed 90%. It is relatively easy to find an existing water turbine design that will optimally harvest the kinetic or potential energy available in almost any river or dam.
However, attempts to extract energy from waves moving across the surface of an ocean or sea are relatively new. Some designs have been proposed in the literature, and described in prior patents. Most are constrained to use in relatively shallow ocean waters where they may be anchored in some manner to the ocean floor. Very few are capable of operating in the deepest parts of the ocean, without benefit of a direct connection to the ocean floor.
Over the years, many devices designed to convert the kinetic and potential energy of ocean waves into electricity, or some other usable form of energy, have been built, patented and proposed. There are many good reasons to engage in such research and development efforts. Ocean waves represent a renewable energy source whose harvesting would not degrade the environment and ecology of the earth. Ocean waves also represent a very concentrated energy source, offering the potential for the harvesting of large amounts of energy from relatively small devices.
There are many potential benefits to developing and using such devices. Replacing the burning of fossil fuels with renewable sources of energy will reduce levels of CO2 entering the atmosphere, and it will reduce the levels of other pollutants in the air such as various sulfur compounds, nitrogen compounds, particulates, etc. Fossil fuels will eventually be exhausted but renewable sources of energy will never be exhausted.
Waves traversing the surface of the ocean represent a repository of a large fraction of the total energy imparted to the earth by the sun. The sun heats the land and the seas and much of this heat energy passes into the atmosphere. Differential heating of the atmosphere across the surface of the earth, in conjunction with the rotation of the earth, causes the atmosphere to move across the surface of the Earth, sometimes at relatively high speeds.
When the atmosphere moves over the surface of the earth's lakes and oceans, it imparts some of its kinetic energy to the waters at the surface of those lakes and oceans, thereby creating waves on the surfaces of said bodies of water. The amplitude of those waves increases as long as the wind blows parallel to the directions in which the waves are propagating. The uninterrupted distance over which the wind blows in a direction parallel to a wave's propagation, imparting increasing amounts of energy to that wave, is called the “fetch” of the wave.
Typical ocean wind waves range from three-tenths of a meter (0.3 m) to five meters (5.0 m) in height. At higher latitudes, ten meter (10.0 m) waves are not uncommon.
The prior art includes a type of wave-energy device capable of operating without an anchor. It includes a unidirectional or bi-directional propeller suspended from a buoy by a shaft or cable. As the buoy moves up and down in response to passing waves, the propeller is moved up and down through the relatively still waters below the surface. This motion of the propeller through relatively still waters compels the propeller to spin. The propeller spins in a constant direction if the propeller is bi-directional but its direction of rotation reverses if the propeller is unidirectional. Such a device does not generate much power.
Even though the force driving the water back and forth through a suspended turbine would be great, the speed of the water's movement is relatively slow. When driven by waves with a height of 5 meters and a period of 8 seconds, the maximum speed of a suspended turbine relative to the water would be two meters per second (2 m/s). At this speed, it would be difficult to extract a significant amount of energy from the flowing water with a simple turbine because the amount of power that can be extracted from a flowing stream of water by a turbine is proportional to the cube of its velocity. In other words,Power=k A v3 
Where “k” is a constant dependent upon the efficiency of a particular turbine's design and implementation, “A” is the cross-sectional area of the stream of water from which power is extracted, and “v” is the velocity of the water.
Since ocean waves rise and fall with a relatively slow speed (the maximum of which is generally only one or two meters per second), it is difficult to extract much energy from the water constrained to flow through a propeller.
However, if the speed of the water constrained to flow through a propeller could be increased, then the power that could be extracted could be increased exponentially. For example, if the speed of the water flowing through the propeller could be increased from a maximum of two (2) to eight (8) meters per second (i.e., a four-fold increase in the water's speed), then the amount of power which could be extracted from the flowing water would increase by a factor of 4×4×4=64, i.e., by a factor of four (4) cubed. The power generated by the turbine could be increased by a factor of 64 by quadrupling the speed of water therethrough.
The following comments about the attributes of surface water waves pertain to those water waves classified as “deep water waves.” Deep water waves move across the surface of a body of water whose depth equals or exceeds one-half of the wavelength of the waves. Furthermore, the following discussion pertains primarily to those deep-water waves classified as “swells.” Swells are water waves having wavelengths varying from about forty (40) to four hundred (400) meters.
The “wavelength” of a deep-water wave is the distance over which the waveform repeats itself, i.e., from wave crest to wave crest. The height to which the wave crest is raised above the corresponding wave trough is the wave height.
Water molecules and other particles contributing to the propagation of deep-water waves have circular as distinguished from elliptical orbits. The radii of the orbits decrease exponentially with increasing depth. The radii become vanishingly small as the depth approaches one-half the wavelength of the waves. This special depth is called the “wave base.” A deep-water wave does not move the water located below the wave base to any significant degree. The water below this depth and any objects floating in it are substantially stationary, even as waves move across the surface overhead.
The depth that defines the wave base for any particular wave or set of waves depends on the wavelength of that wave or set of waves. Waves with longer wavelengths affect the motions of water molecules at greater depths than waves with shorter wavelengths.
The motion of deep water waves is described by:ψx(x,y,t)=reky sin(ωt−kx)+x ψy(x,y,t)=reky cos(ωt−kx)
Notice that in this model every water particle moves in a circular motion. The circle is centered at the water's resting position and has radius of reky where r is the amplitude of the surface wave and −y is the depth below the surface. The radii of these circles decrease exponentially as the depth increases. Thus, even in stormy seas the water below the surface will be quite still.
The power generated by flowing water varies with the cube of the water's speed. The following excerpt explains this:
The instantaneous power density of a flowing incident on an underwater turbine is given by the following equation:
            (              P        A            )        Water    =            1      2        ⁢    ρ    ⁢                  ⁢          U      3        ⁢                  ⁢          (              watts        ⁢                                  ⁢        per        ⁢                                  ⁢        square        ⁢                                  ⁢        meter            )      
where A is the cross-sectional area of flow intercepted by the device, i.e., the area swept by the turbine rotor (in square meters), ρ is the water density in kilograms per cubic meter (1.0 kg/m3 for freshwater and 1.025 kg/m3 for seawater), and U is the current speed in meters per second. For tidal currents, U varies with time in a predictable manner as described previously, and also depends on depth beneath the water surface and position in the channel, as will be described later.
Power density varies with the cube of current velocity. Accordingly, it increases rapidly with current speed.
Deep-water waves move the water, and any objects floating in it, in circular orbits. However, the radii of those orbits decrease to zero as the depth of the water reaches and exceeds the “wave base.” In other words, deep water waves do not significantly affect the location or movement of the water located at depths exceeding the wave base.
This means that when deep-water waves move across the surface of a body of water, those waves create a relative motion between the water at the surface of the body of water; and the water which is at least as deep as the wave base. While the water at the surface is moving in relatively large circular orbits in response to the passage of surface waves, the water below the wave base is not moving at all.
The two primary embodiments of this invention, i.e., the venturi-pinwheel and sea-anchor turbines, exploit this differential movement between the waters at the surface, and in the depths, which is induced by the passage of deep-water waves across the surface of a body of water. This has advantages over other known ocean-stimulated energy systems.
The known tidal flow turbines are large, complex and expensive. Their deployment is difficult. Moreover, large deployments are not possible, i.e., there are a limited number of locations where these devices can operate. They do not generate energy continuously because their energy source is available only during high tide or when tides are changing.
Wave-energy devices located on the shore derive their energy from breaking waves. However, they are aesthetically undesirable and they occupy valuable waterfront real estate. Large deployments are not possible because there are a limited number of locations where these devices can operate. They tend to have a negative impact on the shoreline ecosystem and they do not generate energy continuously.
Wave-energy devices that operate near a shore in relatively shallow water tend to be complex, high-maintenance and expensive. These devices are also aesthetically undesirable as they are usually visible from the shore. They can also disrupt local shipping. There are a limited number of locations where these devices can operate, and large deployments are not practical.
Wave-energy devices that operate off shore in relatively deep waters and are anchored or rest upon the ocean floor are complex, expensive to build and expensive to maintain.
Prior art wave-energy devices that float in the sea are also complex, expensive to build, and expensive to maintain.
The devices disclosed herein are relatively simple, inexpensive to build and maintain, and capable of producing large amounts of energy.
“The venturi effect is an example of Bernoulli's principle, in the case of fluid flow through a tube or pipe with a constriction in it. The fluid velocity must increase through the constriction to satisfy the equation of continuity . . . ”
http://en.wikipedia.org/wiki/Venturi_effect
The continuity equation states that the fluid “mass flow rate”—the amount of fluid traveling through a tube per unit time—must be the same at any cross section of the tube or else there is an accumulation of mass—“mass creation”—and the steady flow assumption is violated. Simply stated:(Mass rate)1=(Mass rate)2 
WhereMass rate=Density×Area×Velocity
This equation reduces top1A1V1=p2A2V2 
Since the fluid is assumed to be incompressible, p is a constant and equation
reduces toA1V1=A2V2 
This is the simple continuity equation for inviscid, incompressible, steady, one-dimensional flow with no leaks. If a flow is viscous, the statement is still valid as long as average values of V1 and V2 across the cross section are used.
By rearranging equation [00052], the following is obtained:V2=(A1/A2)V1 
http://www.centennialofflight.gov/essay/Theories_of_Flight/Conservation/T H8.htm
Venturi tubes increase the speed of water by converting some of its “pressure” energy into directed kinetic energy. The magnitude by which the speed of water moving through a venturi tube is increased is equal to the magnitude by which the cross-sectional area of the channel through which the water must flow is decreased. For example, if the narrow, middle-portion of a venturi tube's channel (i.e. the “throat” of the venturi tube) has a cross-sectional area of only one-fourth that of the venturi tube's inlet, or “mouth,” then the speed of the water flowing through the throat will be four (4) times greater than the speed of the water entering the venturi tube. The cross-sectional area of a circular channel is proportional to the square of its diameter. Accordingly, to increase the speed of the water flowing through the throat of a venturi tube, as compared to the speed of the water entering the tube, by a factor of four; it is only necessary to create a venturi tube with a throat possessing a channel diameter of one-half the diameter of the mouth of the venturi tube.